Split system water heaters are gaining broader acceptance as a more economic and ecologically-friendly alternative to conventional electric resistance water heaters. These systems utilize an external heat source, sometimes called a power module, such as a heat pump. Consequently, water must be circulated within the split system, relatively cool water from the tank to the power module, and heated water from the power module to the tank.
Although split system water heaters are more energy-efficient, split system water heaters can be slower, i.e., take longer to fully heat a tank of water. It is desirable for various reasons to provide thermal stratification within the water heater tank.
Maintaining thermal stratification, e.g., keeping an upper portion hotter than the remainder of the tank, can be difficult in a split system. Water in the tank of a split system tends to mix vertically as the water is circulated between the tank and the power module, creating a uniform temperature mix throughout the tank.
Accordingly, a split system water heater with features for reducing vertical mixing in order to maintain thermal stratification within the tank would be useful.